I haven't used the ad-supported music yet but I did use a Christmas tune from the Free music side.
I wanted to post because I heard something alarming yesterday. Content rights-holders may allow you to use their content for now and they get the ad revenue. What was alarming was that the rights-holders can change their minds anytime in the future. They may decide to let you use the music now and change their mind later.
I'm not sure if that is true or not. If it is, my concern is that if we used the content during the ad-supported time period, the content should stay ad-supported in the future for our original work.